There is known to be an evaporated fuel treatment device comprising a closing valve which is provided on a vapor passage introducing evaporated fuel (Patent Literature #1). In the Patent Literature #1, as an valve opening operation for learning an valve opening start position of the closing valve having a dead zone, disclosed is a method where the operational amount of the closing valve is changed with respect to an open direction at a first speed from zero to a valve closing boundary position in the dead zone, and after passing through the valve closing boundary position, the operational amount is changed with respect to the open direction at a second speed slower than the first speed.